# How can I recognize documents prepared in (La)TeX?

Inspired by a part of this question, this seemed like an interesting question to ask. Advocates of LaTeX often say that you can see the difference in typesetting quality when you look at a document prepared with LaTeX and compare it to something prepared in, say, MS Word. I certainly don't dispute this; I can often tell, but it's hard to put my finger on exactly why. So what are these differences? What are the distinctive features that make a document look like it was prepared in LaTeX, rather than some other system? In other words, if I have a PDF file and I would like to make an educated guess as to whether it was created in LaTeX or not, what should I be looking for? (ignoring any PDF metadata that identifies the creator)

I have my own ideas about this but I'll refrain from self-answering, at least for now, to see what other people may suggest.

-
Since this is a bit subjective and there's no right answer here, should this be community wiki? –  ShreevatsaR Jul 30 '10 at 4:45
Well, I don't really think it's that subjective of a question. If it were, I doubt that multiple answers would be so similar. I'm asking about specific features, which can be identified by anyone with a good eye for typography, and it's not one of those list questions - I'm not trying to accumulate a comprehensive list of differences between LaTeX and Word, for example. So I think there is a case for leaving it non-CW. But I'm not vehemently opposed to changing it to CW, if people think that's appropriate. –  David Z Jul 30 '10 at 5:55

The default style of section headings are often present in LaTeX documents and rarely found in documents produced by systems outside of the TeX family.

Wider margins and a sane number of characters per line are features of most TeX'ed documents and many documents with these features have been TeX'ed.

Those first two can be overridden by a TeX user. The following two, much less so.

Proper ligatures (e.g. the way that the crossbars on "f"s will touch some following letters) are symptomatic of TeX.

My number one sign is relatively few hyphenations and much better looking line justification. You can make a TeX document have a line with bad justification, but it takes effort or bad luck. I've yet to be able to make a word processor have good justification.

-
Right; really badly underfull lines is the most obvious sign to me that it's not been done in (La)TeX. A well typeset document, on the other hand, is harder to pick its origins. –  Will Robertson Jul 30 '10 at 4:14
Before using LaTeX, I routinely fixed my OpenOffice.org documents to use proper ligatures, by manually replacing all occurrences. But then I’m probably one of just a handful of people to do this. –  Konrad Rudolph Jul 30 '10 at 14:20
@Konrad: Ouch!! –  Sharpie Jul 31 '10 at 17:24
I don't know if you'd consider it a word processor, but Adobe InDesign is capable of Knuth-Plass–eque line breaking. –  Ben Alpert Jul 31 '10 at 20:38
Knuth said in an interview that he had heard that InDesign algorithms for whole paragraph spacing is inspired by TeX. –  Leonardo Herrera Aug 4 '10 at 22:48

The first things I look for are Computer Modern fonts and proper ligatures. If the document contains mathematical formulae, the spacing and arrangement of the symbols within looks quite different than the output of, say, Microsoft Equation Editor.

-
I think you'll find Computer Modern fonts being used less and less, though. Proper ligatures certainly. Also an overall feel of aesthetic balance of the page which I'm unable to define more precisely. –  José Figueroa-O'Farrill Aug 4 '10 at 23:53
I find that the math fonts on processors like Word tend to be jarringly different from the usual LaTeX output. Quantifiers in particular tend to be oddly sized compared to surrounding text and overly bold. I'm sure a savvy Word user could fix this, but then again, I've hardly seen any savvy Word users. –  Dennis Jan 27 '14 at 20:59

Lines that are too long. Sad but true.

If you use virtually any word processor to produce fully justified text, they will simply add arbitrarily long inter-word spaces to do that. Latex avoids that, it gives up, outputs a warning and produces a document with a line that is too long.

Of course authors should read the warnings and fix the problem (or at the very least have a look at the final PDF file before sending it to the publisher). Anyway, it is very common to see Latex-prepared articles in conference proceedings with overfull lines.

-
One reason I like the microtype package is that it helps reduce the likelihood of this. (Not to 0, sadly.) –  vanden Aug 19 '10 at 2:36

There are two things that always stand out for me, even on a printed page where I can't check what fonts were used (although it's fairly easy to identify CM fonts by sight, at least compared with Arial, Times, etc.). One is the quality of math, as described by Blake. The other, that makes me use TeX for even mathless writing, is the fact that nothing I've seen so far is able to make the inter-word spacing of fully justified text look anywhere near as clean as TeX does it (and for most documents I don't like the look of ragged right text).

-

One almost-giveaway is the usage of Computer Modern, the font Knuth designed for TeX. (Though I've had friends ask me how to use Computer Modern in non-TeX programs and many people also change the fonts in (Xe|La)?TeX to be different from the default.)

-
• Proper small caps
• Optical Sizes (small text looks more robust and headlines look more skinny)
• Floated figures with proper figure captions
• Whitespace (noobs will get this wrong however)
• Wide use of numerical cross-references (word processors make this cumbersome to use)
• Margin Kerning
• Text blocks centered vertically on the page
• Lines on opposing pages not on the same baseline
• Sentence spacing. Longer space after period (not with `\frenchspacing`)
• General consistency
-
While I agree with most of your points, LaTeX (by default) does not center text blocks vertically on the page - that would be rather a sign of Word & Co. –  lockstep Sep 3 '10 at 20:12